Veins are thin-walled and contain one-way valves that control blood flow. Normally, the valves open to allow blood to flow into the deeper veins and close to prevent back-flow into the superficial veins. When the valves are malfunctioning or only partially functioning, however, they no longer prevent the back-flow of blood into the superficial veins. As a result, venous pressure builds at the site of the faulty valves. Because the veins are thin walled and not able to withstand the increased pressure, they become what are known as varicose veins which are veins that are dilated, tortuous or engorged.
In particular, varicose veins of the lower extremities are one of the most common medical conditions of the adult population. It is estimated that varicose veins affect approximately 25% of adult females and 10% of males. Symptoms include discomfort, aching of the legs, itching, cosmetic deformities, and swelling. If left untreated, varicose veins may cause medical complications such as bleeding, phlebitis, ulcerations, thrombi and lipodermatosclerosis.
Traditional treatments for varicosities include both temporary and permanent techniques. Temporary treatments involve use of compression stockings and elevation of the diseased extremities. While providing temporary relief of symptoms, these techniques do not correct the underlying cause that is the faulty valves. Permanent treatments include surgical excision of the diseased segments, ambulatory phlebectomy, and occlusion of the vein through thermal means.
Surgical excision requires general anesthesia and a long recovery period. Even with its high clinical success rate, surgical excision is rapidly becoming an outmoded technique due to the high costs of treatment and complication risks from surgery. Ambulatory phlebectomy involves avulsion of the varicose vein segment using multiple stab incisions through the skin. The procedure is done on an outpatient basis, but is still relatively expensive due to the length of time required to perform the procedure.
Minimally invasive thermal treatments for venous insufficiency eliminate the need for general anesthesia and have relatively short recovery times. Endovascular thermal energy therapy is a relatively new treatment technique for venous reflux diseases. With this technique, thermal energy in the form of laser or radio frequency (RF) energy is delivered by an energy delivery device that is percutaneously inserted into the diseased vein prior to energy delivery. In a laser therapy, an optical fiber is used as the energy delivery device whereas in an RF therapy, RF electrodes are used as the energy delivery device. The procedure for the thermal energy therapy involves inserting an introducer catheter or sheath and advancing it to within a few centimeters of the sapheno-femoral junction of the greater saphenous vein. In the case of laser therapy, once the introducer catheter is properly positioned, a flexible optical fiber is inserted into the lumen of the catheter or sheath and advanced until the distal fiber tip is near the catheter tip but still protected within the catheter lumen.
Once the energy delivery device is positioned within the vein, the tissue immediately surrounding the diseased vessel segment is subjected to numerous needle punctures to make percutaneous injections of a tumescent anesthetic agent. The injections, typically Lidocaine with or without epinephrine, are administered under ultrasonic guidance along the entire length of the greater saphenous vein into the perivenous space. The tumescent injections perform several functions. First, the anesthetic injection inhibits pain caused from the application of energy to the vein. Second, the injection reduces the diameter of the vein to facilitate efficient energy transmission to the vessel wall. Third, the tumescent injection also provides a barrier between the vessel and the adjacent tissue and nerve structures, which restricts the heat damage to only the vessel itself and prevents non-target tissue damage. After the anesthetic injections are made through multiple puncture sites, the energy delivery device is withdrawn as thermal energy is transferred to the inner vein wall causing cell necrosis and eventual vein collapse.
For thermal treatment, the injection of tumescent anesthesia through multiple punctures along the diseased segment is considered a standard and necessary step in the treatment protocol. However, there are several disadvantages associated with such a conventional method of administering local anesthesia injections. The anesthetic injection process is cumbersome and is the most time-consuming step in the treatment procedure because of the number of punctures that has to be made. Typically, injections are administered along the entire length of the greater saphenous vein in 2-3 cm increments. The total injection length varies but is usually between 30 and 40 cm.
Although these minimally invasive thermal treatments have been shown to be effective and safe in eliminating the cause of varicosities, they have procedural shortcomings and complications that make them less than ideal. As discussed above, administration of tumescent anesthesia along the vein segment being treated requires careful administration and significant preparation time. In addition, reported thermal treatment complications include pain for up to ten days following treatment, extensive bruising caused by vessel perforations, paresthesias, deep vein thrombosis and skin burns. The energy generator and disposable devices necessary to perform the procedure are expensive and require capital investment by the practitioner. Another drawback of thermal treatment of venous disease is the delivery device, which limits treatment to veins of a diameter that will accommodate the device. Very tortuous veins cannot be treated by thermal ablation because the catheter cannot successfully navigate the vein path.
Chemical occlusion, also known as sclerotherapy, is an in-office procedure involving the injection of an irritant chemical directly into the vein. The drug is delivered either through direct injections with a small gauge needle or more recently using a catheter placed in the target vein. The chemical acts upon the inner lining of the vein walls causing them to occlude and block blood flow. The use of liquid sclerosing agents to treat varicosities has been utilized for decades, but has traditionally been limited to veins with diameters less than 5 mm.
Sclerotherapy to treat larger diameter veins has not been widely used due mainly to recommended volume limit of the drug and reported failure rates. Sufficient drug must be delivered to the treatment zone to fully displace the blood. A typical sclerosant, such as 3% sodium tetradecyl sulfate, is volume limited to a maximum of 10 cc per treatment, making it difficult to treat larger veins. Catheter-directed sclerotherapy has been attempted in larger veins such as the Great Saphenous Vein using liquid sclerosant. Although initially successful, long-term failure rates are reportedly high, due to inadequate concentrations of drug being delivered to the vessel to cause durable closure and permanent destruction of the vein. It is also postulated that blood flow in larger veins prevents the sclerosant from reaching the vessel wall in sufficient concentration to effectively destroy the inner vessel wall lining to occlude the vessel, resulting in a relatively low treatment success rate.
To minimize the dilution of the agent by blood, some practitioners have utilized methods of emptying as much blood volume as possible from the vein being treated. Vein emptying may be performed by placing the patient in a Trendelenberg position with the target leg higher than the torso. Emptying may also be facilitated by the use of manual compression using either compression bandages or finger compression at the proximal and distal ends of the vein. These techniques, while lowering the overall blood volume in the vessel, are time-consuming, require additional personnel to maintain compression during the procedure, are uncomfortable to the patient, and often result in incomplete blood removal and inconsistent treatment results.
Another sclerotherapy treatment that has recently emerged involves the use of a foamed sclerosant to treat larger veins. A liquid sclerosing agent can be converted to a foam agent by forcing gas into the liquid, whereby creating microbubbles. Foam has several advantages over liquid sclerosant. Foamed sclerosing agents provide an increased concentration of the sclerosing agent against the vessel wall. The theory is that the foam displaces the blood in the vessel as the sclerosant is carried on the exterior of the bubble. The foam contacts the vein wall delivering high concentrations of the drug to the vein wall while minimizing the amount of drug introduced in to the patient. Theoretically, these microbubbles contact and adhere more effectively to the vessel wall than liquid because of their increased surface tension. Increased concentration of sclerosant allows the practitioner to use lesser amounts than with liquid sclerosant, whereby decreasing potential complications associated with larger drug volumes. A further advantage of foam is that as it is injected, the foam displaces the blood locally, whereby minimizing the possibility of ineffective closure due to dilution of the sclerosant by the blood. The displacement of blood allows the practitioner to use less sclerosant.
When treating a vein with foam, some form of image guidance must be used to insure foam reaches the intended location and does not enter the deep venous system through the connecting perforating and tributary veins. The gas bubbles in the foam make it visible under ultrasound or a contrast agent may be mixed with the foam for visualization using fluoroscopy.
While foam has been demonstrated to be more effective in vein closure compared with infused liquid, it may cause significant neurological and systemic complications if it travels to the arterial system. The gas bubbles that escape the superficial vessel and migrate to the deep venous system are normally filtered out by the lung, but if the patient has a patent foramen ovale (septal defect in the heart present in approximately one-fourth the population), bubbles may pass from the venous system into the arterial system, resulting in temporary visual problems, reduced cognitive functioning and other more serious side effects such as stroke. The procedure must be closely monitored to prevent the expanding foam from entry into the deep venous system through tributaries or perforating veins.
Some sclerotherapy delivery devices utilize one or more occlusion elements to isolate the treatment area, whereby minimizing dilution of the drug and reducing the total volume necessary for treatment. Once the device is properly positioned, the balloons or other occlusion elements are inflated, creating an isolated vein segment to which the sclerosant is delivered. The balloons temporarily occlude blood flow through the isolated segment and also prevent the migration of drug into the deep venous system. These devices, while effective in isolating the treatment area, are complicated devices which are expensive to manufacture and require additional training to use. In addition, complications can occur when the sclerosant is injected into the isolated segment. The pressure within the isolated segment, by the injection of sclerosant, may force the sclerosant into the deep venous system through perforator veins. This situation can lead to deep vein thrombosis, and in the case of foam sclerosant, may cause microbubbles to travel to the pulmonary system.
Therefore, it is desirable to provide an effective method of treating venous reflux utilizing a fluid sclerosant agent that targets the vessel wall without dilution. The method should avoid the associated complications of foam migration to the deep venous system. The method should not require emptying the vessel of blood. The method should be able to treat large diameter veins without having to isolate vein segments using complicated occlusion devices. It is cumbersome and time-consuming to monitor the sclerosant as it is delivered to ensure injected volumes are insufficient to migrate through the perforators into the deep venous system. A method which eliminates or minimizes monitoring and instead uses controlled volumes is desirable. Further, it is desirable to provide a method of vein closure that does not require complicated and expensive equipment and delivery devices, and is simple and fast for the practitioner. It would be advantageous for the method to be performed using a catheter based system to avoid the time and complications associated with direct stick injections. Optimally, the use of time-consuming tumescent anesthesia would be eliminated with this method. Finally, it would be advantageous to provide a method of treatment that minimizes the total volume sclerosant required for the procedure by directing concentrated drug directly at the vessel wall.